Electrical cables of the metal clad type typically include an outer metallic sheath having an insulated jacket thereover and a plurality of individually insulated electrical conductors extending therethrough. The outer metallic sheath may include helical windings along its length to increase the flexibility of the cable. Metal clad cables of this type may be used for transmitting power and/or control signals for use in distribution centers, motors, panel boards and numerous other electrical and electromechanical apparatus.
Connectors which terminate such metal clad cables are designed for connecting the cable to an electrical box. Two requirements of this type of connector is that the connector provide an effective electrical ground between the metallic sheath of the cable and the electrical box and also provide a seal between the connector and the cable itself. The electrical connector art has seen a wide variety of connector structures which, in one fashion or another, achieve both results.
U.S. Pat. No. 4,490,576, issued Dec. 25, 1984 describes a connector for terminating jacketed metal clad cable where a grounding ring is employed to make mechanical and electrical engagement with the metallic sheath of the cable and establish continuity between the cable sheath and the connector itself. Grounding rings of this type typically include a plurality of inwardly projecting fingers which extend into contact with the metallic sheath of the cable upon insertion of the cable into the connector thus establishing electrical engagement therewith. While the fingers of the grounding ring are slightly resilient in order to permit accommodation of the cable therethrough, the fingers must provide sufficient clearance so as to not totally prevent insertion of the cable. Thus, the grounding ring must be dimensioned precisely to accommodate a cable sheath of a given diameter. Employing a cable sheath having a larger diameter then is appropriate for the grounding ring will result in the cable not being readily insertable into the connector. Similarly, employing a cable having a sheath of lesser diameter will result in an ineffective ground.
U S. Pat. No. 4,692,562, issued Sept. 8, 1987 addresses the need for providing an effective grounding and sealing member which will accommodate cables of different sizes. The connector described in the '562 patent employs a connector body having a frustoconically shaped internal bore and includes a correspondingly shaped grounding ring and sealing member. In its initial position, sufficient clearance is provided to permit insertion of the cable into the connector without engagement of the cable sheath with fingers of the grounding ring. Thus, a wide range of cable sizes may be accommodated in the connector. After cable insertion, a gland nut is tightened down forcing the grounding ring against the frustoconical bore and into engagement with the cable sheath.
While providing for accommodation of a wider range of cable sizes than the connector of the '576 patent, the connector of the '562 patent fails to provide initial ground contact between the grounding ring and the metallic sheath upon initial insertion of the cable into the connector. Thus, in situations where the cable gland nut inadvertently is not tightened down or not sufficiently tightened down to establish ground contact, ground connection will not be achieved between the cable and the electrical box thereby resulting in a potentially hazardous situation.
It is therefore desirable to provide an electrical connector which accommodates a wide range of sizes of metal clad cable and which provides initial grounding engagement with the cable upon insertion into the connector.